Air filter



oct. 1 4, 1941.

C. A. CAMPBELL AIR FILTER Filed Jan. 1'2, 1939 QQQQQI; v DEH-:IEDE

Patented Oct. 14, 1941 riufriiirl Charles A. ,(l'ampbell, Watertown,V NI! Y., assigner 'to The .New York BalerCcnipaiIYLr/e corpo-'- ration of New Jersey Application January-12, 1939, Seria/L hlm-250,662 e cigainlfs.A (C1. lea-49.).

' The present inventionfrelatesf'to air ltere,-A and especially to filters of the-type employedftofprotect the vautomatic valves of railwayA airV brake systems (for example', triple valve'sjvent valves, application valves, etc.) "from dust, scale and otliger harmful substances which enter the brake p1pe.

V'A well'knownv example of the type of Viiltering device to which the presentimprovements re-V late, although not limitedthereto, is'thetubular filterwhich is mounted in-"fthe pipe 'bracketfof' theAB freight brake now'standa'rd on American railways.- This lter unit is interposed between the brake pipe on the one hand, andthe piston chambers of the service and emergencypdrtionsofthe AB triple valve on the other, so as'- tolter the air passing to the latter from ther brakepip'e. The present standard form of the above-nientionedlter comprises innerand outer, foraminous, tubular retaining or shell members Vof metal, anda wool-fabric' iiltercoveringgwrapped: around the inner tubular member. Betweenthe fabric covering and the outer foraminous tubular member is packed a massV of curled hair forthe purpose of liiltering out coarse foreign` substances from the a-ir and also preventing direct impingement ofv foreign substances against the lfabric cover onthe inner tube.A The iilterunitis lalso provided, at each end, with an annular felt washer which is located between the tubular shell members and restsyagainst the' mass -`of curled hair, the washervbeing held inpl'ace' by annular series: of bent-over lugs on the ends of theinner andV `outer tubular retaining members.

- When the' above-describedgflter unit or' as- 35 semblyfis in place in its chamber inthe pipe bracket of the AB brake, lthe unit is clamped: between'la pair of opposed, narrow, annular seal-` ing ribs,`of V'sh aped transverse-sectional form, provided on the bracket structure; these annular ribs engagingthe pairof felt end washersV ori-the filter unit toform tight seals therewith, so tha-t allair owing from `the brake pipe* to the valve willpass throughy th'ecurl'ed hair, thelter fabric and the felt endwashers.V It hasbeen found lin practice, howeverfthat, due tofthe `re silientnature oflthe curled hair pack whichi supports the felt endvwashers, these. Washers in a shortl time are forced inwardlyrtowards eachA other by the clamping pressure tfosuchan eX- tent that the inner edges of theannul'ar feltj' end washers arey drawn away from theinner tubular member. This permits foreignn` 'substancesfin thebrake pipe air' Ato shortfcvircuiebetween;.me

felt end`v washers and* theL inner fabric-'-covered 57; unitremoved from the pipe bracketE tubularmember;` whereupon Athey passv to1 the valve mechanism.

VA.furtherserious. objection: to-theabove method of supporting the felt end washersaisvthat, once the curleslihairV pack? .takes a permanenty set, vthe endzrwashers become` distorted to such' an: extent tha-mythen the lteriunit is removed forycleaning and: thenVA re-app-iied to the: valve bracketl chamber or recess.' imperfect end sealing-is invariablyI encountered. Asa result, leakage of unfiltered'` .airA occurs' vbetween* the'.l end vwashers antttheannular sealing ribsionthe bracket.v

' .'[Yhel 'present inventionprovid'es-a'lter unitlcon'-v struction ofthe: above-type which completely overcomes-thelvdef'e'cts; mentioned and.' insures against leakage l of 'unfiltered or incompletely filtered air around'o'r throughthevlter unit` evenunder the: most severeoperating` conditions.. In general, this" is accomplished by incorporating rigi'd'means inftheflter si'jructurev which. serve' to ad'equa'tel'yE support and' retain the Vfelt endl washers ini place independently of the curledhair pack, or other filtering AmediumY used for the purpose. VThis permits thecurled hair pack to be'made ofan'ydesired resili'encewithout aecting4r the" `airi-ti'ght end' seals' between the' washers and' the sealing' ribs*l onthe'` pipe bracket; and the same 'is' true even though 4thehairV pack be ycompletelyydestroyed. or lose its' resilience.- A furtherfeature ofl'theimproved construction. is the direct" coactibnofthe washer supporting meanslwth the fabricgcovered, inner retainer tube. to preventv allipossibility ofv passage of unfiltered'.` or incom- 'pletely filtered airv between the end washers and?. the. fabric. covered tube, and thence into` the. valve: parts. l

The improved construction also provides ai muchmore rigid? iilterA unit, whereby likelihood ofk distortion" thereof is minimized and. proper` functioningy ofV the various parts, when the'unitr issin userli'siassured;

The practical embodiment of the invention'` unit chamber or recessV characteristic yoftliisv bracket structure. The' improved lterf unitiv isshown, inlongitudinal axial'section; clamp'edinv place in its chamber in the pipe' bracket.

Fig. 2 isj anendview of the' iilter.ciaidzridggev or Fig. 3 is an enlarged fragmentary section taken on line 3-3 of Fig. 2.

In Fig. 1 of the drawing, I indicates a part of the AB pipe bracket. This has a generally cylindrical casing portion 2 providing a chamber or recess 3 in which the improved filter unit is shown clamped in operative position. The annular space 4 surrounding the filter unit communicates directly with the brake pipe.

Passage 6, opening into one end of chamber 3, leads to the piston chamber of the service p01*-, tion of the AB valve. The opposite end of chame ber 3 is closed by an adjustable and removable plug 1 threaded into the bracket.

ton chamber of the emergency portion of the valve. A narrow, annular sealing rib or bead 9,

Small port 8 in this plug offers communication with the'pis.-V

V-shaped in transverse section, isV provided at' the inner end of chamber 3 and a similanrib.

II is formed on plug 1. The extremities of the filter cartridge, which is clamped between' and has its ends sealed by annular ribs 9 iand II as a result of adjustment of plug 1, are located in the reduced end portions I2, I3 of chamber 3.

The improved filter cartridge, which is of the same construction at each end, is of cylindrical form and comprises inner and outer, foraminated, tubular retaining or shell members I4, I5, respectively, each preferably formed of brass tubing. These tubular retaining members I4, I5, which are of the same length, are arranged concentrically one within theV other to provide space therebetween for the reception of air straining material. formed. at its opposite ends with short, annular, imperforate webs I6 which are connected together by an extended annular foraminated portion I1 having perforations I8 therein. The outer retainer member or casing I is similarly constructed with imperforate, annular end webs I9 and an extended foraminated central portion having perforations 2 I. K

Each end web I6 of the inner retainer or core member I5Y is formed, as by rolling, with an annular external 4rib 22 which is outwardly-V curved in transverse section. A similar internal annular rib 23 is provided on each end web I9 ofthe outer retainer or body Inemberl I5. Each annular rib 23 is disposed somewhat out of transverse alinement with the corresponding annular rib 22 on inner retainerlr4, rib 23 bein'goffset slightly with reference to rib 22 lengthwise of,l the lter unit and towards the middle thereof. As best shown in Fig. 2,A each end ofinner retainer member I4 is formed with an annular series of bent-over lugs 24, and the ends of outer retainer member I5 are provided with similar lugs 25. Y

l Closelyencircling inner retaining memberoI4 and covering the openings I8 therein is a sleeve 26 of porous material, preferably woolifabric, such as felt. Felt covering 26 extends. at each end soas to cover the imperforate end webIB on Acore member I4, and. partiallyoverlap end lugs 24 (see Fig. 3 particularly). Thus there is formed near each end of cover 26 Aan annular rib 21 which surrounds and closely conforms to rib 22 on core member I4.

Located between inner and outer vretainer members I4 and I5, at each end thereof, is a substantially rigid, metal annulus or thrust member 28 having a ilat, disk-shaped body portion and a cylindrical hub portion 29 projecting outwardly from the rim of the central opening in the annulus. The outer rim of thrust mem- Inner retainer member or core I4 is;`

ber 28 seats on the annular supporting ledge formed by rib 23 on outer retainer member I5. Hub or inner rim portion 29 of the thrust member, which has an internal diameter preferably slightly less than the external diameter of annular rib 22 on inner retainer I4, fits snugly around the felt-covered, end web portion I 6 of the retainer member. Hub 29 is connected to the body portion of the thrust member by an annular, transversely-curved or flared portion 30 and the latter seats on rib 2'I of felt cover 26 which is supported in turn by rib 22 on inner retainer I4.

Each thrust member 28 carries a thick annu- ;larfelt sealing washer 3| which fills the space between 'outer retainer I5 and hub 29 of the thrust member. Felt sleeve 26 at each end is flared outwardly to form an annular flange 32 engaging the outer end of hub 29 and the outer face of washer 3I. Bent-over lugs 24 and 25, on inner and outer retainer members I4 and I5, retain felt washer 3| in place and, by ltheir compression' of the `washer and flange 32 of felt sleeve26, tightly force thrust member 28 against both annularribV 23 on the outer retainer,` and the annular seat formed by rib 22 on the inner retainer and the interposed annular portion 33 of the felt sleeve. I'hus the flared inner rim portion 30 of thrust member 28 ,provides an annulartapered surface 34 which surrounds and coactsv with the annular tapered surface 35 on rib 22 to tightly Wedge or clamp and compress the Aannular portion 33 of the felt sleeve therebetween. This forms an effective annular seal at this point.

Lugs 24 not only secure the end of the felt sleeve against the end of hub 29, but in so doing effect an annular seal between the felt flange 32 and the hub end. The annular space between the ends of the inner series of lugs 24 and the outer series of lugs 25 provides an annular free portion 36 onveach Washer 3I. These annular portions 36, -36 of the Washers are clamped in tight sealing engagement with annular pipe v bracketV ribs 9 and II and the opposed thrust members 28, 28, as appears clearly in Fig. 1.

The annulanspace 31 between felt sleeve 28 and outer lshell I5 is packed with` curled hair 38, or any other suitable straining medium, the curled hair being confined at the ends ofthe unit by thrust members 28, 28. l V

A In assembling thelter unit described,` the `iirst operatmn is to place the cylindrical feltsleeve 26 on the innerretainer tube I4. At this time the lugs 24 at each end of tube I4 are not yet bent over butvare in their originalstraight form extending axially from the ends of retainer I4. After felt sleeve l26 isin place, the end of the sleeve is held against the annular series'of straight lugs 24 at one end of `tube I4 and a thrust member 28 slipped over the felt covered endof the'vtube. After tightly pressing thrust member 28 against the annular portion 33 of felt sleeve 26 `and its annular supporting rib 22 on the inner retainer, a p air of diametrically-opposed lugs 24 is `bentover the end of hub 29 of the .thrust member.,V In so doing, the end of felt sleevev 26 is flared outwardly to form the flange 32 abutting against the end of hub 29 and thrust member 28 is firmly secured in place on retainer member I4.

The above assembly is then inserted as a unit into one end vof the outer retainer member I5, the lugs 25 of which are straight at this time,

Auntil therim of thrust member 28 engages annular rib 235cmouterretainermember I-;A Following thisgwasherfBluis inserted in place and then. the remaining lugsl 24and alllv of the lugs 2.5 are bent over to clamp. the part's'rmly'together 'at one end' of the assembly.

The assembled 'endof the 4filter isnow pla-ced downward' and/the' annular space 3-:l between outer retainer member l5 and felt-covered inner retainer member .I4 packed with..` the mass'. of curled'h'a'ir 38'.. After this,..the .other 'thrust memberv 28iis slippedfover the opposite end of felt-coveredv inner retainer |4'v and. a" washer 3'| placed'on the thrust member. 'When this. thrust member has been tightly pressed inwardly againstjann'ular rib. 23 onthe outer retainer |5,'

and against annular portion 33 of felt sleeve 26 and its supporting rib 22 on inner retainer I4, the lugs 24 and 25 are bent over to firmly clamp all of the parts together at this end of the unit.

The improved lter unit, when inserted and clamped in place in the air brake pipe bracket as shown in Fig. 1, provides a filtering device which completely precludes entrance of abrasive dust into the brake valve parts from the brake pipe under all conditions encountered in operation. Compressed air entering annular space 4 from the brake pipe, in order to reach passage 6 and port 8 leading to the valve parts, must pass first through the foraminous outer retainer member l5, curled hair pack 38, felt sleeve 26 and foraminous inner retainer member I4. The completely ltered air, from which all dust has been removed by curled hair 38 and felt sleeve 26, then flows from the interior of inner retainer member I4 to the valve parts.

The lter cartridge presents a rugged, unitary structure which is quite rigid and therefore not easily distorted so as to interfere with its proper functioning in use. Each thrust member 28 forms a rigid element which is rigidly mounted in the end of the unit so as to fully support its felt washer 3| entirely independently of the curled hair pack 38. Consequently, the degree of resilience of the hair pack or the absence of such resilience, or even the complete destruction of the hair pack, will have no elfect upon airtight sealing of end washers 3|, 3| with annular ribs 9, and thrust members 28, 28. Each thrust member 28 provides a flat, rigid annular surface which always supports its washer 3| in its normal iiat condition and thus prevents distortion or displacement thereof in use. Therefore, even after the unit has been removed for cleaning and is replaced again, there is always complete annular sealing engagement between end washers 3|, 3|, annular bracket ribs 9, Il, and thrust members 28, 28. This prevents all possibility of unfiltered or incompletely filtered air leaking between the end washers and sealing ribs 9 and Il, or between the washers and thrust members 28, 28, and then flowing to the valve parts.

Leakage of unfiltered or incompletely filtered air between the ends of fabric sleeve 26 and felt end washers 3|, 3| even though the curled hair body 38 be completely destroyed, is positively prevented at each end of the lter by the annular seal formed between the fabric sleeve and the inner'rim of the thrust member 28 by the direct coaction of these parts with the rib 22 on inner retainer I4, as already described. In this connection it is important to note that the greater the end thrust applied to felt end washers 3|, 3|, by annular bracket ribs 9, in clamping the lilter unit in place, the greater will be the pressureexertedvby each .thrust'memberA 28 to clam-p- .portion .33t of they Vfabric sleeve against rilr122, thus'.insuring'.maintenancey of the annular s'eal'atl 'thispoint ati all times. Further guarantee. .against` leakage around rthe ends' of faliricA sleeve 2.6 andi 'of maintenance of thesleeve ends: Viii-.place on .inner v:retainer |'4 is afforded by the. 'clampingand sealing of eachv end flange 32 of the.ffabric'sleeve 'againstthe endl Tof the hull ofthe thrustfmember v28by'l'ugs 24;l

isclaimedis. 1 l.

v1. In aafrlter. unit,lthe combination of a foraminousttiibular'body member; `a foraminous tubularcore memb'erf arranged within saidb'ody memberfi'n spaced relation thereto,1"said body 'member being provided with an internal projection spaced inwardly of one end of the unit and said core member being formed with an annular external rib also spaced inwardly of said end of the unit; a porous fabric sleeve on the core member covering the openings therein; a rigid annular thrust member arranged between the body and core members with its outer rim bearing on said projection on the body member and the sleeve tightly clamped between the inner rim of the thrust member and the rib on the core member; an annular Washer between the body and core members and engaging the outer face of the thrust member; and bent-over lugs on the adjoining ends of the body and core members for clamping said parts in assembled and sealed relation.

2. In a lter unit, the combination of a foraminous tubular body member; a foraminous tubular core member located Within said body member in spaced relation thereto, said members at one end of the unit being provided inwardly thereof and between the members with a pair of opposed annular ribs; a porous fabric sleeve mounted on said core member and covering the openings therein, said sleeve having an annular end flange; a rigid annular thrust member located between said members with its outer rim engaging the rib on the body member and the sleeve tightly clamped between the inner rim of the thrust member and the rib on the core member; an annular washer between the body and core members and engaging the outer face of the thrust member, said thrust member having an outwardly extending hub with its outer end sealing with said sleeve flange; and bentover lugs on the adjoining ends of the body and core members for clamping said parts in assembled and sealed relation.

3. The combination in a lter of a foraminous tubular shell member; a sleeve of pervious material mounted on the shell member and covering the openings therein; a rigid annular thrust member rigidly mounted on the sleeve on each end of the shell member and having annular sealing engagement between its inner rim and said sleeve, each of said thrust members including a disk-like washer-receiving portion; a compressible washer sealing against the outer face of each of said thrust members and means for tclamping said parts in assembled and sealed relaion.

4. The combination in a filter of a foraminous tubular shell member having an annular external enlargement near one end thereof; a sleeve of pervious material mounted on the shell member and covering the openings therein and also said enlargement; a rigid annular thrust member rigidly mounted on said sleeve on said end of the shell member with the sleeve clamped between annular coacting surfaces on the inner rim of said thrust member and said annularv enlargement on the shell member whereby to provide a tight annular seal between the sleeve and the thrust member, said thrust having a disklike washer-receiving portion; a compressible annular washer sealed against the outer face of the thrust member and means for clamping said parts in assembled and sealed relation.

5. The combination as claimed in claim 4 further characterized in that at least one of said annular enacting sleeve-clamping surfaces on said inner rim of the thrust member and said annular enlargement on the shell member is tapered, whereby to insure tight gripping of the sleeve between said surfaces and an annular seal betweenl the thrust member and the sleeve.

6. The combination in a filter unit of a foraminous tubular body member; a foraminous tubular core member located within said body member in spaced relation thereto; annular washers of compressible material secured between said body and core members at the ends thereof; and separate rigid means, located between said members at each end thereof and each fxedly secured independently of the other to at least one of said members, for supporting said annular end washers against inward movement towards each other.

CHARLES A. CAMPBELL. 

